PINNING EFFECT OF SOLUTE ATOMS ON GRAIN-BOUNDARY DISLOCATION DISSOCIATION

The dissociation of extrinsic grain boundary dislocations (EGBDs) in A l, Al-Mg and Al-Mg-Sn alloys was studied at various temperatures. Whil e EGBDs were commonly observed in low- and high-angle boundaries in th e alloy materials deformed to small strains, they could only be seen i n low-angle grain boundaries in Al. Annealing of the lightly deformed alloy samples at 100 or 150 degrees C led to the disappearance of the EGBDs with critical disappearance kinetics depending on grain boundary composition. A modified EGBD dissociation mechanism incorporating a s olute drag effect has been developed in this work. Predictions based o n the model agree reasonably well with the observed thermal behavior o f the EGBDs in the three Al alloys. (C) 1997 Elsevier Science S.A.